1. Field of the Invention
The present invention relates to kitchen appliances and, more particularly, to control of a heating element.
2. Prior Art
Electric coffee makers can have a hot plate or heating plate to keep a coffee pot warm. Some coffee makers have an adjustable warming plate. Thermal cut off (TCO) fuses are used to prevent the heating plates from overheating. Some coffee makers have electronic circuitry and a timer for programmed brewing. A potential problem with some coffee makers is that the TCO fuses can sometimes fail in a closed or shorted position. Even when two TCOs are used in series, if they come from the same manufacturing batch of TCO fuses, they may have the same failure problems. There is a need to provide a more dependable heating element control which can overcome the potential problem of TCOs in a coffee maker failing.
In accordance with one embodiment of the present invention, a kitchen appliance is provided having a heating element and a control for controlling supply of electricity to the heating element. The control comprises a temperature sensor comprising a thermistor or thermocouple; an electronic controller electrically connected to the temperature sensor; and a user actuatable input connected to the electronic controller for selecting upper and lower temperatures for cycling OFF and ON supply of electricity to the heating element. For all of the user selectable upper temperatures, the electronic controller is adapted to turn OFF supply of electricity to the heating element when an output from the temperature sensor indicates a sensed temperature which is equal to or above the selected upper temperature plus a first predetermined temperature value.
In accordance with another embodiment of the present invention, a kitchen appliance is provided having a heating element and a control for controlling supply of electricity to the heating element. The control comprises a temperature sensor adapted to output a sensed temperature signal; an electronic controller connected to the temperature sensor; and a user actuatable input connected to the electronic controller for selecting a temperature range of the heating element. The electronic controller is adapted to interrupt supply of electricity to the heating element upon the sensed temperature signal from the temperature sensor being either about 0 volts or about an input voltage into the temperature sensor.
In accordance with another embodiment of the present invention, an electric coffee maker is provided having a water heater, a heating plate for a coffee pot, the heating plate having an electric calrod, and a heating plate control. The heating plate control comprises a first thermal cut off fuse adapted to open at a first temperature; a second thermal cut off fuse adapted to open at a second different temperature, the first and second fuses being connected in series between the calrod and a supply of electricity; an electronic controller adapted to open and close a path between the supply of electricity and the first fuse; and a temperature sensor connected to the electronic controller. The electronic controller is adapted to open and close the path between the supply of electricity and the first fuse based upon an output from the temperature sensor.